Life is an exercise to express the InExpressible.

Today one new label is added. "Database". There are set of articles planned in this category. Today is the first one. Most of us know, in RDBMS, database table has primary key and foreign key. Any idea about other types of key? Below tables describes all database keys and relations among them.

Primary

Unique

Surrogate

Foreign

Composite

Simple

1

Primary

1

1

May be

May be

May be

May be

2

Unique

May be

1

May be

May be

May be

May be

3

Surrogate

May be

1

1

May be

0

1

4

Foreign

0

May be

0

1

May be

May be

5

Composite

May be

May be

0

May be

1

0

6

Simple

May be

May be

0

May be

0

1

7

Super

0

1

0

0

May be

May be

8

Minimal super

May be

1

0

0

May be

May be

9

Tirival Super

May be

1

0

May be

1

0

10

Candidate

May be

1

May be

May be

May be

May be

11

Alternate

0

1

1

May be

May be

May be

12

Natural

May be

1

0

May be

1

Super

Minaml super

Tirival Super

Candidate

Alternate

Natural

1

Primary

May be

May be

0

1

0

May be

2

Unique

1

May be

May be

1

May be

May be

3

Surrogate

0

0

0

May be

May be

0

4

Foreign

May be

May be

0

0

0

0

5

Composite

May be

May be

1

1

May be

0

6

Simple

0

May be

0

May be

May be

May be

7

Super

1

May be

1

0

0

8

Minimal super

1

1

0

1

May be

May be

9

Tirival Super

1

0

1

1

May be

0

10

Candidate

1

1

1

1

May be

May be

11

Alternate

1

1

0

1

1

May be

12

Natural

0

1

May be

1

The above table should be read, row wise

For example 1st row:

Is primary key is unique? 1 = Yes

Is it surrogate? The surrogate key can become primary key. However the primary key is not always surrogate. So answer "May be"

and so on. Here 1 = Yes and 0 = No

Here are some key points about database keys

The primary key cannot be NULL

The unique key can be NULL

The primary key is always unique

All unique keys are candidate key to become primary key

Primary key can be one of the candidate key or it can be surrogate key

The candidate key, who is not primary key is alternate key.

If surrogate key is primary key, then all candidate keys are alternate keys.

Simple key and composite key are mutually exclusive.

The compound key should have at least two simple keys

The composite key is extension of compound key

Natural key and domain key are synonyms.

Composite key, compound key, aggregate key and concatenated key. All are in a way same.

I have posted few mindmaps on this blog: IPSec , IMS and SIP, ANDSFToday one more. It is about IoT. "Internet of Things" is a buzzword. In fact, IoT and 5G are like two sides of single coin. There are many standards related to IoT defined by various standarisation bodies. These standards are for wired connection and wireless connection. The wireless connection is also referred as Low Power Wide Area Network (LP-WAN). It is further categorizes licensed spectrum and Non-licensed spectrum. IoT is also about many protocols used. The IoT application uses database with specific set of features.

As per WikipediaA mind map is a diagram used to visually organize information. A mind map is hierarchical and shows relationships among pieces of the whole.[1] It is often created around a single concept, drawn as an image in the center of a blank page, to which associated representations of ideas such as images, words and parts of words are added. Major ideas are connected directly to the central concept, and other ideas branch out from those.